In CMOS image sensors, it is common to supply power to the pixel array from an on-chip voltage regulator. The analog-to-digital converter in each pixel typically requires a certain minimum voltage, typically 1.2V, to operate correctly. However, the IR voltage drop varies with the distance of a given pixel from the supply point, and this becomes exacerbated as the array size increases. One approach is to control the voltage regulator by an analog feedback loop from the farthest pixel, but such a feedback loop can have stability problems owing to the parasitics (resistance, capacitance, and some inductance) of the long remote sensing route.
A further problem in known arrangements is that, in order to deal with high frequency load variations, it may be necessary for the voltage regulator to have an external compensation component in the form of a relatively large capacitance. This may be provided by a capacitor external to the chip, and thus may require extra parts and assembly and connection operations.